1. Field of the Invention
The present invention relates to the field of display technology, and in particular to a liquid crystal display panel.
2. The Related Arts
A liquid crystal display panel is generally made up of a color filter (CF) substrate, a thin-film transistor (TFT) array substrate, and a liquid crystal layer arranged between the two substrates and the operation principle is that a drive voltage is applied to the two glass substrates to control liquid crystal molecules of the liquid crystal layer to rotate in order to refract out light from a backlight module to generate an image. Based on the way of orientating liquid crystal, the liquid crystal display panels of the main stream market can be classified as the following types: vertical alignment (VA), twisted nematic (TN) or super twisted nematic (STN), in-plane switching (IPS), and fringe field switching (FFS).
For the VA mode, a liquid crystal display device is generally made up of upper and lower substrates and negative liquid crystal molecules interposed between the two substrates. A transparent conductor layer (indium tin oxide, ITO) is formed on an inside surface of each of the upper and lower substrates in order to form a vertical electric field. Negative liquid crystal is embedded between the two transparent conductor layers so that the liquid crystal molecules are oriented perpendicular to the surfaces of the substrate when no vertical electric field applies thereto, and the liquid crystal molecules are oriented at a specific direction and are eventually lined up in a direction perpendicular to the electric field when a vertical electric field applies thereto.
The VA mode has advantages in respect of image displaying including high contrast and high transmittance. However, since the VA mode adopts liquid crystal of vertical rotation, the difference of birefringence of the liquid crystal modules is relatively large, leading to a poor view angle and a relatively severe issue of color shifting at a large view angle. Often, multi-domain VA techniques are adopted, in which a sub-pixel is divided into multiple areas and the liquid crystal molecules of the areas are made to rotate at different angles when a voltage is applied thereto in order to alleviate the color shifting issue.
With the advance of technology, a polymer sustained vertical alignment (PSVA) mode that requires no alignment film has been proposed. As shown in FIG. 1, a PSVA mode liquid crystal display panel comprises a first substrate 100, a second substrate 200 that is opposite to the first substrate 100, a liquid crystal layer 300 interposed between the first substrate 100 and the second substrate 200, pixel electrodes 110 that are arranged on the first substrate 100 and spaced from each other; and a common electrode 210 that is arranged on the a side of the second substrate 200 that is adjacent to the liquid crystal layer 300 and covers the second substrate 200. The liquid crystal layer 300 is composed of a number of liquid crystal molecules 310 and a number of reactive monomers 320. After the first substrate 100 and the second substrate 200 are combined together and the liquid crystal layer 300 is filled, a voltage is applied to the common electrode 210 and the pixel electrodes 110 to have the liquid crystal molecules 310 tilt following the direction of slits of the electrode pixels 310. Then, ultraviolet (US) rays are applied for irradiation so as to cause reaction of the reactive monomers 32 for forming reactant projections 330 attached to surfaces of the pixel electrodes 110 and the common electrode 210, as shown in FIG. 2, wherein the reactant projections 330 function to constrain the liquid crystal molecules 310 to form a pre-tilt angle at a predetermined direction. As shown in FIG. 3, when a vertical electric field is applied, the liquid crystal molecules 310 are caused to orient at a specific direction and eventually lined up at a direction perpendicular to the electric field.
The PSVA mode has the characteristics of fast response and high contrast. However, due to the inclusion of the reactive monomers in the liquid crystal layer to participate in the alignment process, the choice of the liquid crystal is greatly constrained, readily leading to an issue of dependency, and severe requirements may be imposed on the manufacturing process and the materials used.
The IPS mode and FFS mode have the characteristics of having wide view angles; however contrast is poor as compared to the VA mode.